feat(v2): satmachineclient maintenance pass — v2 admin schema (P7)

Updates the LP-facing client extension to work against the v2 admin schema
(per-machine dca_clients, leg_type-discriminated dca_payments, settlement
audit trail) and strips the dead v1 code paths.

Maintenance-mode framing: the richer LP UI is migrating to ~/dev/webapp.
This extension now provides a minimal stable read-mostly surface so
existing LP installs don't break against the v2 admin schema.

models.py — rewrite:
  + PerMachinePosition: LP's position at a single machine
  ~ ClientDashboardSummary: now aggregates across all the LP's machines
    and exposes per-machine breakdown in `positions` field
  ~ ClientTransaction: gains machine_id + machine_npub + settlement_id;
    drops transaction_type / lamassu_transaction_id (v1 fields)
  ~ leg_type discriminator on ClientTransaction so the LP can tell DCA,
    operator-initiated balance-settle, and auto-forward legs apart
  + UpdateClientAutoforward: LPs control their own autoforward setting
  - ClientDashboardSummaryAPI, ClientTransactionAPI: deleted (GTQ-only
    parallel "API" models that duplicated the internal ones)
  - ClientPreferences, ClientRegistrationData, UpdateClientSettings:
    deleted (registration + settings are operator-controlled in v2)

crud.py — rewrite:
  + _fetch_user_clients: all dca_clients rows for the LP, joined with
    dca_machines for display metadata
  + _position_for_client: per-machine aggregation helper
  + get_client_dashboard_summary: aggregates positions + sums sats/fiat
    + computes cost basis on fiat-spent (not gross deposits)
  + get_client_transactions: filters to LP-visible leg_types
    (dca / settlement / autoforward); optional machine_id filter
  + update_lp_autoforward: LP self-manages autoforward across all their
    machine positions
  - get_client_analytics (300+ lines of date-parsing pretzels): deleted;
    webapp will own analytics
  - register_dca_client: deleted (admin owns registration in v2)
  - update_client_dca_settings: deleted (admin owns DCA mode/limits)
  - Lamassu-era status='confirmed' (now 'completed'), transaction_type
    column refs, lamassu_transaction_id column refs: all gone

views_api.py — rewrite to 3 endpoints:
  GET /api/v1/dca-client/positions       (aggregated dashboard)
  GET /api/v1/dca-client/transactions    (filterable history)
  PUT /api/v1/dca-client/autoforward     (LP self-manages forwarding)

All require_admin_key on the LP's wallet. Old registration / settings
/ analytics endpoints removed.

Files deleted:
  tasks.py — empty stub ("No background tasks needed")
  transaction_processor.py — empty stub ("No transaction processing")

README.md gains a status banner pointing LP audience at webapp.

.gitignore gains `data/` + sqlite db files + __pycache__ to prevent
LNbits runtime artifacts (auth keys, dev DBs) from being committed.

4 routes registered. Zero ruff errors across the extension.

Refs: aiolabs/satmachineadmin#9 — completes P7

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -1,4 +1,6 @@
-__pycache__
-node_modules
-.mypy_cache
-.venv
+# LNbits runtime data — auth keys, DB files, etc. Never commit.
+data/
+*.sqlite3
+*.sqlite3-journal
+__pycache__/
+*.pyc